What Marijuana Does To Your Body And Brain

It's 4/20. For those not in the know, "4/20" is the unofficial holiday for pot smokers and marijuana legalization activists around the world to celebrate by lighting up on April 20.

The Huffington Post's Ryan Grim traced the term back to 1971. A group of California high school friends, known as the "Waldos" used "4/20" as a code word to refer to the time of the day when they would smoke outside of school.

This year, for the first time, residents of Colorado, Washington, and Uruguay can celebrate the day with legal recreational marijuana.

The plant, best-known for its "feel-good" effects and touted for its uses for multiple diseases, can also be damaging to our bodies and minds.

The high you get from marijuana mostly comes from a chemical called Tetrahydrocannabinol, also known as THC, which is found in varying potency in different strains of cannabis.

Most of THC's effects happen in the brain, where the chemical interacts with receptors on brain cells called cannabinoid receptors. Our bodies actually make chemicals very similar to THC, which are used in normal brain function and development. THC co-opts these natural pathways to produce most of its effects.